1. Field of the Invention
This invention relates to a disc cartridge having housed therein a disc-shaped recording medium, such as an optical disc.
This application claims priority of Japanese Patent Application No. 2004-013603, filed on Jan. 21, 2004, the entirety of which is incorporated by reference herein.
2. Description of Related Art
Up to now, a disc cartridge, housing a disc-shaped recording medium, such as an optical disc, and loaded on a recording and/or reproducing apparatus with the disc-shaped recording medium rotatably housed therein, is in widespread use. With such disc cartridge, the disc-shaped recording medium is housed in a main body unit of the cartridge to protect the disc-shaped recording medium to assure facilitated lading/unloading of the disc for the recording and/or reproducing apparatus.
With this disc cartridge, in which the disc-shaped recording medium, housed in the main body unit of the cartridge, needs to be loadable on the recording and/or reproducing apparatus, the main body unit of the cartridge is provided with a driving opening for facing a turntable of a disc rotating driving mechanism for rotationally driving the disc-shaped recording medium, and with a recording and/or reproducing aperture for exposing a portion of the signal recording area of the disc-shaped recording medium to outside across the inner and outer rims thereof.
The disc cartridge is provided with a shutter member for opening/closing at least the recording and/or reproducing aperture for protecting the disc-shaped recording medium housed in the main body unit of the cartridge.
With this disc cartridge, the main body unit of the cartridge, housing the disc-shaped recording medium therein, is made up by upper and lower halves, molded from synthetic resin, and unified together by abutting and connecting the upper and lower halves together.
The disc cartridge, used as a recording medium for the recording and/or reproducing apparatus, is loaded on the recording and/or reproducing apparatus, with the lower surface of the main body unit of the cartridge as the loading reference surface. Thus, the lower half, defining the lower surface of the main body unit of the cartridge, is provided with a driving opening, a recording and/or reproducing aperture and a positioning hole engaged by a positioning pin provided to the recording and/or reproducing apparatus for setting the loading position. The outer rims of the upper and lower halves 3, 4 are provided with upstanding peripheral wall sections abutted to each other to form an outer peripheral wall section of the main body unit of the cartridge, and housing forming wall sections on the radially inner parts of the upstanding peripheral wall sections which, when abutted together, delimit a disc housing. These housing forming wall sections are formed in continuation or in non-continuation to the inner rim of the upstanding peripheral wall sections.
Meanwhile, with the disc-shaped recording medium, such as an optical disc, the tendency is to increase the recording density and to reduce the disc diameter in keeping up with the increased recording density. As the disc-shaped recording medium is reduced in size, the disc cartridge, housing the disc-shaped recording medium, also is to be reduced in size.
As the size of the disc cartridge is reduced, the disc cartridge is also reduced in thickness. Since the disc cartridge has to be reduced in size as the inner space for housing the disc-shaped recording medium is increased, attempts are being made to reduce the thickness of the upper and lower halves making up the main body unit of the cartridge.
The positioning holes, formed in the lower half, are formed in left-hand and right-hand areas, delimited between the housing forming wall sections and the upstanding peripheral wall sections, forming the outer peripheral wall. These areas are also reduced in thickness as is the planar surface of the lower half forming the bottom surface of the disc housing.
With the disc cartridge, reduced in size, the area delimited by the housing forming wall sections and the upstanding peripheral wall sections, is also small, such that the positioning holes are formed in proximity to the housing forming wall sections and the upstanding peripheral wall sections.
These positioning holes are engaged by positioning pins provided to the cartridge loading section of the disc recording and/or reproducing apparatus. The positioning holes are engaged by positioning pins by the disc cartridge being lowered from an elevated position onto the cartridge loading section. The disc cartridge is not lowered at this time in a horizontal position with respect to the cartridge loading section but is mostly lowered towards the cartridge loading section as the disc cartridge is inclined relative to the positioning pins. If the disc cartridge is lowered as it is inclined relative to the positioning pins, the risk is high that, as the positioning pins are engaged in the positioning holes, the distal ends of the positioning pins compress against and damage the housing forming wall sections or the upstanding peripheral wall sections. In particular, the distal ends of the positioning pins are tapered to provide for facilitated engagement thereof in the positioning holes. The housing forming wall sections or the upstanding peripheral wall sections may readily be damaged by contact with such positioning pins. With the disc cartridge, reduced in size, in which the housing forming wall sections or the upstanding peripheral wall sections are reduced in thickness as are other portions, these wall sections may readily be damaged by abutment against the positioning pins. In case the housing forming wall sections are damaged, the disc-shaped recording medium, housed in the disc housing, may not be protected properly.
In addition, as the distal ends of the positioning pins are engaged in the positioning holes, the risk is high that the thin-walled portions, carrying the positioning holes, tend to be deformed, with the result that the loading position cannot be set accurately.
The risk is also high that, in the course of the engagement of the positioning pins in the positioning holes, the positioning pins act strongly on the rim of the positioning holes, with the result that the main body unit of the cartridge may be subjected to damages, such as cracks.
With this in mind, the Patent Publication 1 discloses a solution in which a thick-walled portion is provided on the rim of the positioning holes. In the solution of the Patent Publication 1, only the rim of the positioning holes is provided with the thick-walled portion, so that it is not possible to assure sufficient strength of the vicinity of the positioning holes. In particular, it is difficult with this solution to assure sufficient strength of the main body unit of the cartridge, reduced in size and thickness, and to enable the disc cartridge to be loaded in position on the carridge loading section.
[Patent Publication 1] Japanese Laid-Open Patent Publication H-11-144424